The purpose of this study is to determine the effect of ichthyotoxins from Prymnesium parvum and Gymnodinium breve on the ionic permeability of lipid bilayer membranes in terms of selectivity to specific ions, binding parameters of the toxins, and chemical identity of the various toxic fractions isolated by chromatographic methods. We will also determine if the active toxins have an effect on membrane dependent metabolic functions of culture cells with defined membrane characteristics such as the active transport of low molecular weight substrates, cell to cell contact inhibition and cell division. The above methodologies will be used to monitor the occurrence of new algal toxins in field-collected specimens and to determine their spectrum of activity.